The forest diggers

Some of the coast's most important dependencies are also its least visible, worked by animals almost nobody sees. Recall that nearly every tree and shrub here feeds a fungus at its roots and is fed in return — the mycorrhizal partnership without which these poor soils would grow very little (see plant-partnerships). Many of those fungi fruit not as toadstools above the ground but as truffle-like bodies below it, sealed in the soil, and a fungus underground has exactly the problem of a plant rooted to the spot: it cannot move its own spores. So it strikes the same kind of deal the plants do, and pays in food.

The couriers are a guild of small, snuffling, night-digging marsupials. On the Sunshine Coast these are the bandicoots — the northern brown bandicoot (Isoodon macrourus, still reasonably common) and the long-nosed bandicoot (Perameles nasuta) — and, more localised and more precarious, the long-nosed potoroo (Potorous tridactylus), a rabbit-sized cousin of the kangaroos. (The true arch-diggers of this tribe, the bettongs, live out in the drier country and do not occur on the Sunshine Coast, so read them as the outback example, not a local one.) These animals sniff out the buried fungi, dig them up and eat them, and carry the spores off in their gut to be dropped, still alive, across the forest floor. In eating the fungus they plant it. A potoroo or a bandicoot working the ground at night, turning and aerating the soil with thousands of little conical diggings — bioturbation, the low art of the plough — is not merely feeding itself; it is sowing the underground partner on which the forest's nutrition depends (see species-dependence). Take the digger away, and over time you thin the fungal network and weaken the trees that lean on it, in a slow unravelling almost no one would trace back to a missing marsupial.

Which is more or less what has happened across much of the continent. The digging marsupials sit squarely in the size range the red fox and the feral cat find easiest to kill — the critical weight range that has borne the brunt of Australia's mammal extinctions — and the introduced hunters have pulled them down to scattered remnants or wiped them out altogether (see biological-invasion). The Sunshine Coast's larger, better-protected bushlands still keep some of theirs, for now, but their thinning is one more thread drawn softly out of the web. It is a loss felt not up at the surface, where we might notice, but down in the roots, where hardly anyone thinks to look — which is exactly what makes the forest diggers so easy to lose and so worth reading for.